Venous thromboembolism (VTE) is a major national health problem, with over 275,000 incident cases annually. Our long-term objective is to determine the epidemiology of VTE in the community. Our specific aims are: Aim 1: To extend our analysis of trends in the incidence of VTE by updating our Olmsted County, MN inception cohort with a first lifetime DVT or pulmonary embolism (PE) from 1966-1997 through 12/31/2005 in order to test the hypotheses that, over the most recent 10-year period (1996-2005) which reflects the current standard of VTE prophylaxis, the overall incidence of VTE is unchanged while the incidence of PE among postpartum women is lower compared to earlier periods. Aim 2: To continue our comprehensive analysis of risk factors for VTE by performing 5 nested case-control studies to test diabetes mellitus, hypertension, hyperlipidemia, lipid lowering therapy, infection, (3-blocker therapy and angiotensin-converting enzyme (ACE) inhibitor therapy; type and duration of prophylaxis (hospitalized surgery and medical cases); type and duration of anesthesia (surgery cases); indicators of immobility, lack of self-preservation, activities of daily living and specific nursing home location (nursing home cases); and tumor site, tumor stage, tumor progression, presence of metastases, location of metastases, and site of local tumor invasion (cancer cases) as independent risk factors for VTE, both overall (2a) as well as among patients hospitalized for major surgery (2b) or acute medical illness (2c), patients confined to a nursing home (2d), and cancer patients (2e). Aim 3: To collect interval history data in order to extend our analysis of independent predictors of VTE recurrence to include the effects of interim exposures between the incident and recurrent VTE events, and the introduction of low molecular weight heparin therapy (LMWH), on the hazard of VTE recurrence. This data will provide insights regarding the effect of new prophylaxis drugs on VTE incidence and why some but not most high-risk patients develop VTE, and test the effect of outpatient LMWH therapy on VTE recurrence.